A compound represented by the formula (I) or a salt thereof; and an agent for protecting a brain/neuronal cell or a therapeutic agent for sleep disorder comprising the compound or salt: wherein Z represents an oxygen or sulfur; R.sup.1 represents an aryl or heterocyclic group which may be substituted, provided that R.sup.1 is not a 3-ethyl-6-methoxy-2-methyl-5-naphthalen-1-yl group; R.sup.1a represents a hydrogen atom, a hydrocarbon group which may be substituted, a hydroxyl group or the like; R.sup.2 represents a piperidin-1,4-diyl or piperazin-1,4-diyl which may be substituted; R.sup.3 represents a bivalent group which is formed by removing two hydrogen atoms from a benzene ring or 6-membered aromatic heterocyclic ring which may have a substituent, provided that R.sup.3 is not a pyridazin-3,6-diyl; and R.sup.4 represents a group which is formed by removing one hydrogen atom from a benzene ring or 5- to 6-membered heterocyclic ring which may be substituted, provided that the substituent on the heterocyclic ring is not a phenylethyl group which may be substituted when Z is sulfur. ##STR00001##

Claim:

The invention claimed is:

1. A compound represented by the formula (I): ##STR00016## wherein Z represents an oxygen, R.sup.1 represents an isoxazolyl, pyridyl or pyridazinyl, each of which maybe substituted with one or more substituents selected from a group consisting of a C.sub.1-6 alkyl which may be halogenated or oxolated, a C.sub.1-6 alkoxy which may be halogenated or oxolated, a C.sub.1-6 acylamino which may be halogenated or oxolated,a N--(C.sub.1-6alkyl)C.sub.1-6 acylamino, a C.sub.1-6 acyl which may be halogenated or oxolated, a C.sub.1-6 alkylamino, a di-C.sub.1-6 alkylamino, a C.sub.1-6 alkenyl which may be halogenated or oxolated, a C.sub.1-6 alkynyl which may be halogenated oroxolated, a C.sub.1-6 alkyloxycarbonyl, a carbamoyl, carboxy, a C.sub.1-6 alkylsulfonylamide which may be halogenated or oxolated, a C.sub.1-6 alkylthio which may be halogenated or oxolated, a C.sub.1-6 alkylsulfinyl which may be halogenated or oxolated,amino, hydroxyl, a halogen, nitrile, 2-oxopyrrolidin-1-yl, imidazolyl and pyrazolyl, provided that 5-ethyl-2-methoxy-6-methyl-3-pyridinyl is excluded, R.sup.1a represents a hydrogen atom, R.sup.2 represents piperazin-1,4-diyl which may be substitutedwith one or more substituents selected from a group consisting of a C.sub.1-6 alkyl which may be halogenated or oxolated, a C.sub.1-6 alkoxy which may be halogenated or oxolated, a C.sub.1-6 acylamino which may be halogenated or oxolated, aN--(C.sub.1-6alkyl) C.sub.1-6 acylamino, a C.sub.1-6 acyl which may be halogenated or oxolated, a C.sub.1-6 alkylamino, a di-C.sub.1-6 alkylamino, a C.sub.1-6 alkenyl which may be halogenated or oxolated, a C.sub.1-6 alkynyl which may be halogenated oroxolated, a C.sub.1-6 alkyloxycarbonyl, a carbamoyl, carboxy, a C.sub.1-6 alkylsulfonylamide which may be halogenated or oxolated, a C.sub.1-6 alkylthio which may be halogenated or oxolated, a C.sub.1-6 alkylsulfinyl which may be halogenated or oxolated,amino, hydroxyl, a halogen, nitrile and 2-oxopyrrolidin-1-yl, R.sup.3 represents a divalent group formed by removing two hydrogen atoms from a benzene or 6-membered aromatic heterocyclic ring containing 1 to 4 heteroatoms selected from oxygen atom,sulfur atom and nitrogen atom in addition to carbon atom, with pyridazin-3,6-diyl excluded, each of which may have one or more substituents selected from a group consisting of a C.sub.1-6 alkyl which may be halogenated or oxolated, a C.sub.1-6 alkoxywhich may be halogenated or oxolated, a C.sub.1-6 acylamino which may be halogenated or oxolated, a N--(C.sub.1-6alkyl)C.sub.1-6 acylamino, a C.sub.1-6 acyl which may be halogenated or oxolated, a C.sub.1-6 alkylamino, a di-C.sub.1-6 alkylamino, aC.sub.1-6 alkenyl which may be halogenated or oxolated, a C.sub.1-6 alkynyl which may be halogenated or oxolated, a C.sub.1-6 alkyloxycarbonyl, a carbamoyl, carboxy, a C.sub.1-6 alkylsulfonylamide which may be halogenated or oxolated, a C.sub.1-6alkylthio which may be halogenated or oxolated, a C.sub.1-6 alkylsulfinyl which may be halogenated or oxolated, amino, hydroxy, a halogen and nitrile, and R.sup.4 represents a phenyl, thienyl or furyl, each of which may be substituted with one or moresubstituents selected from a group consisting of a C.sub.1-6 alkyl which may be halogenated or oxolated, a C.sub.1-6 alkoxy which may be halogenated or oxolated, a C.sub.1-6 acylamino which may be halogenated or oxolated, a N--(C.sub.1-6alkyl)C.sub.1-6acylamino, a C.sub.1-6 acyl which may be halogenated or oxolated, a C.sub.1-6 alkylamino, a di-C.sub.1-6 alkylamino, a C.sub.1-6 alkenyl which may be halogenated or oxolated, a C.sub.1-6 alkynyl which may be halogenated or oxolated, a C.sub.1-6alkyloxycarbonyl, a carbamoyl, carboxy, a C.sub.1-6 alkylsulfonylamide which may be halogenated or oxolated, a C.sub.1-6 alkylthio which may be halogenated or oxolated, a C.sub.1-6 alkylsulfinyl which may be halogenated or oxolated, amino, hydroxy, ahalogen and nitrile, or a salt thereof.

2. The compound according to claim 1, wherein the divalent group represented by R.sup.3 is a group formed by removing two hydrogen atoms from a benzene, pyridine, pyrimidine, pyrazine, triazine, oxazine or thiazine, or a salt thereof.

3. The compound according to claim 1, wherein R.sup.1 is isoxazolyl which may be substituted with one or more C.sub.1-6 alkyl, pyridyl which may be substituted with one or more C.sub.1-6 acylamino, or pyridazinyl.

4. The compound according to claim 1, wherein R.sup.3 is a divalent group represented by formula: ##STR00017## wherein ring A represents benzene, pyridine, pyrimidine, pyrazine, triazine, oxazine or thiazine ring, or a salt thereof.

5. The compound according to claim 1, wherein R.sup.3 is 1,3-phenylene, 1,4-phenylene, pyridin-2,4-diyl or pyridin-2,5-diyl, each of which may have one or more substituents selected from a group consisting of a C.sub.1-6 alkyl which may behalogenated or oxolated, a C.sub.1-6 alkoxy which may be halogenated or oxolated, a C.sub.1-6 acylamino which may be halogenated or oxolated, a N--(C.sub.1-6 alkyl)C.sub.1-6 acylamino, a C.sub.1-6 acyl which may be halogenated or oxolated, a C.sub.1-6alkylamino, a di-C.sub.1-6 alkylamino, a C.sub.1-6 alkenyl which may be halogenated or oxolated, a C.sub.1-6 alkynyl which may be halogenated or oxolated, a C.sub.1-6 alkyloxycarbonyl, carbamoyl, carboxy, a C.sub.1-6 alkylsulfonylamide which may behalogenated or oxolated, a C.sub.1-6 alkylthio which may be halogenated or oxolated, a C.sub.1-6 alkylsulfinyl which may be halogenated or oxolated, amino, hydroxy, a halogen and nitrile.

7. A pharmaceutical composition comprising the compound according to claim 1 or a salt thereof.

8. A fatty acid amide hydrolase inhibitor comprising a compound according to claim 1, or a salt thereof.

9. A therapeutic agent for sleep disorder, anxiety or depression, or an analgesic agent comprising a compound according to claim 1, or a salt thereof.

10. A method for treating sleep disorder, anxiety or depression, or a method for pain relief, which comprises administering to a subject in need thereof an effective amount of a compound according to claim 1, or a salt thereof.

11. The compound according to claim 1, wherein R.sup.1 represents an isoxazolyl which may be substituted with one or more substituents selected from C.sub.1-6 alkyl, a pyridyl which may be substituted with one or more C.sub.1-6 acylamino, or apyridazinyl, R.sup.2 represents a piperazin-1,4-diyl, R.sup.3 is a divalent group represented by formula: ##STR00018## wherein ring A represents benzene, pyridine, pyrimidine, pyrazine, triazine, oxazine or thiazine ring, and R.sup.4 represents a phenyl,thienyl or furyl, each of which may be substituted with one or more substituents selected from a group consisting of a C.sub.1-6 alkyl which may be halogenated or oxolated, a C.sub.1-6 alkoxy which may be halogenated or oxolated, a C.sub.1-6 acylaminowhich may be halogenated or oxolated, a N--(C.sub.1-6 alkyl)C.sub.1-6 acylamino, a C.sub.1-6 acyl which may be halogenated or oxolated, a C.sub.1-6 alkylamino, a di-C.sub.1-6 alkylamino, a C.sub.1-6 alkenyl which may be halogenated or oxolated, aC.sub.1-6 alkynyl which may be halogenated or oxolated, a C.sub.1-6 alkyloxycarbonyl, carbamoyl, carboxy, a C.sub.1-6 alkylsulfonylamide which may be halogenated or oxolated, a C.sub.1-6 alkylthio which may be halogenated or oxolated, a C.sub.1-6alkylsulfinyl which may be halogenated or oxolated, amino, hydroxyl, a halogen and nitrile, or a salt thereof.